/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hadoop.hbase.regionserver;

import org.apache.hbase.thirdparty.com.google.common.annotations.VisibleForTesting;

import java.util.Random;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.HBaseInterfaceAudience;
import org.apache.hadoop.hbase.HConstants;
import org.apache.yetus.audience.InterfaceAudience;
import org.apache.hadoop.hbase.client.TableDescriptor;

/**
 * A {@link RegionSplitPolicy} implementation which splits a region
 * as soon as any of its store files exceeds a maximum configurable size.
 * <p>
 * This is the default split policy. From 0.94.0 on the default split policy has
 * changed to {@link IncreasingToUpperBoundRegionSplitPolicy}
 * </p>
 */
@InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.CONFIG)
public class ConstantSizeRegionSplitPolicy extends RegionSplitPolicy {
    private static final Random RANDOM = new Random();

    private long desiredMaxFileSize;
    private double jitterRate;

    @Override
    protected void configureForRegion(HRegion region) {
        super.configureForRegion(region);
        Configuration conf = getConf();
        TableDescriptor desc = region.getTableDescriptor();
        if(desc != null) {
            this.desiredMaxFileSize = desc.getMaxFileSize();
        }
        if(this.desiredMaxFileSize <= 0) {
            this.desiredMaxFileSize = conf.getLong(HConstants.HREGION_MAX_FILESIZE, HConstants.DEFAULT_MAX_FILE_SIZE);
        }
        double jitter = conf.getDouble("hbase.hregion.max.filesize.jitter", 0.25D);
        this.jitterRate = (RANDOM.nextFloat() - 0.5D) * jitter;
        long jitterValue = (long) (this.desiredMaxFileSize * this.jitterRate);
        // make sure the long value won't overflow with jitter
        if(this.jitterRate > 0 && jitterValue > (Long.MAX_VALUE - this.desiredMaxFileSize)) {
            this.desiredMaxFileSize = Long.MAX_VALUE;
        } else {
            this.desiredMaxFileSize += jitterValue;
        }
    }

    @Override
    protected boolean shouldSplit() {
        boolean force = region.shouldForceSplit();
        boolean foundABigStore = false;

        for(HStore store : region.getStores()) {
            // If any of the stores are unable to split (eg they contain reference files)
            // then don't split
            if((!store.canSplit())) {
                return false;
            }

            // Mark if any store is big enough
            if(store.getSize() > desiredMaxFileSize) {
                foundABigStore = true;
            }
        }

        return foundABigStore || force;
    }

    long getDesiredMaxFileSize() {
        return desiredMaxFileSize;
    }

    @VisibleForTesting
    public boolean positiveJitterRate() {
        return this.jitterRate > 0;
    }
}
